Sphygmomanometers are commonly known in the field of medical diagnostic medicine as devices that are used by a clinician, a caregiver or a patient in order to measure the arterial blood pressure (ABP) of the patient. In brief, these pressure measuring devices commonly include a flexible inflatable sleeve or cuff that is wrapped around the limb of a patient, such as the arm or leg, and are attached to inflation means, such as for example, a pneumatic bulb or pump. A gage mechanism that is attached to the apparatus detects fluid pressure changes within the sleeve interior that provide diastolic and systolic pressure readings when used in combination with a stethoscope.
Recently, Applicants' have devised an improved gage mechanism that is useful for such devices, as well as other pressure measuring apparatus. This mechanism, as described in U.S. Pat. No. 5,966,829, the entire contents of which are herein incorporated by reference, utilizes a thin helically wound ribbon spring member that is secured at one end to an axial shaft member and to a fixed support of the apparatus of the remaining end. The shaft member is translatable and retains a measurement indicator and a dial face with indicia at one end while the remaining end of the translatable shaft member is placed into a position that can receive the output of a diaphragm or other pressure responsive element. As the sleeve inflates and deflates, the diaphragm moves and the shaft member is subsequently caused to move in an axial direction. Due to the constraint of the helically wound ribbon spring, however, the shaft member is also caused to rotate about its axis and circumferential movement is therefore also imparted to the indicating member relative to the dial face and its indicia. The above gage mechanism is elegant in its manufacture and relatively simple in design yet produces highly repeatable and accurate results with literally any parameter output in addition to pressure. Moreover, the mechanism is very compact as compared to typical gage movement mechanisms used for these purpose that are akin in their complexity to Swiss watches, requiring many more parts with higher tolerances, increased weight and a larger profile/envelope in order to retain the mechanism.
In later versions of the above gage mechanism, it was determined that the above axial design, due to its simplicity and ease of manufacture, could be placed in a housing that could be directly attached to the inflatable sleeve and moreover could be fluidly interconnected to the interior of the sleeve without the need of hoses or tubing. This concept is described in greater detail in U.S. Pat. No. 6,615,666, the entire contents of which are also incorporated by reference.
It is a general desire in the medical instrument field to be able to improve the shock bearing characteristics of blood pressure measuring apparatus, particularly the above-noted gage mechanism. Invariably, these apparatus are prone to drops from tables or other surfaces and/or other shock or impact type loads may be imparted thereupon that can prematurely disable or destroy their effectiveness. Recent attempts, as described in the afore incorporated U.S. Pat. No. 6,615,666, have further included the provision of a releasably or integrally mounted peripheral bumper that is placed in overlaying relation onto a portion of an upper portion of the gage housing, as well as the addition of a circumferential channel to the engagement end of the gage housing that mates with a socket of the inflatable sleeve. While these attempts have improved the overall durability of the blood pressure measuring apparatus, including the contained gage mechanism, from certain localized types of impact or shock loads, there is a continuing need to further improve the ability of these pressure measuring apparatus to generally withstand these types of loads.